The present invention relates to means and method for examining fecal matter to determine the presence of ova or eggs of parasites such as might be found in the fecal matter. Especially when the infestation is small, and also with some variations in the physical condition of feces, it is important that a good separation of ova from the feces be obtained. And at the same time it is highly desirable that the steps in preparing the feces samples, malodorous and esthetically upleasant at unpleasant shall be made as few, as simple, and as non-contaminating to the technician and the laboratory as possible. Obviously, it is desirable that the receptacles and auxiliary apparatus be disposable after one use in order to avoid the unpleasantness of clean-up. Yet, for a laboratory handling many samples each day, as is common in active veterinary hospitals, disposable apparatus must not only cost very little, but must be environmentally acceptable. In the present marketplace, these considerations and others clearly dictate that the apparatus shall be of inexpensive plastic such as polyethylene, and shall have the least possible number and complexity of components.
For many years the preferred laboratory technique, in numerous minor variations, has been the use of a float-or-sink process, in which a liquid of density between that of the ova and that of the other fecal matter is stirred into the feces sample, and opportunity is provided for the ova to separate by flotation from the other matter. The ova, having floated to the top of the liquid, are then transferred to a microscope slide, as by touching the cover glass to the surface of the liquid. Under the microscope the kinds of ova can be discerned, and the seriousness of the infestation estimated by rough counting of the number of each kind of ova seen in the field.
This prior art process has been improved in several ways, but still suffers several problems, not only esthetic, but also of a degree of unreliability or inaccuracy.
Older improvements were (1) Centrifuging the float-or-sink mixture to achieve a sharp separation. (2) Filtering the float-or-sink mixture from the mixture receptacle into another receptacle by pouring the mixture through a strainer, and both metallic and non-metallic strainers have been used. Movement through the strainer is by gravity. In the second receptacle the ova, largely freed from the other fecal matter, float to the top, and are transferred as before mentioned, to a microscope slide cover glass. Pertinent references are:
COLES, E. H. "Veterinary Clinical Pathology," W. B. Saunders Co., Philadelphia, 1967, pg 332 PA0 CHANDLER, A. C. "Introduction to Parasitology" 8th Ed., John Wiley & Sons, N.Y. 1949, pg 249 - 251 PA0 BODDIE, G. F. "Diagnostic Methods in Veterinary Medicine," Lippincott, Phildadelphia, 1953, pg 309 PA0 HOSKINS, H. P. et al, Ed., "Canine Medicine" American Veterinary Publications, Inc., Santa Barbara, California, 1959, pg 605, 606.
Such methods are described in a most recent improvement, which is disclosed in U.S. Pat. No. 3,819,045 issued in June 25, 1974 to Robert J. Greenwald, in which is disclosed a combination of apparatus elements, including a shallow cup means for original receipt of feces sample, a cover means for use during transport of the sample to laboratory, an open tube means for thrusting into said cup means whereby to extend it vertically and to form a treatment receptacle, a piston means of diameter to fit snugly into said tube, the piston having its face perforated, and having a piston-rod-like handle extending axially. In use, at the laboratory, the transport cover is removed from the shallow cup, the open tube is thrust into the well of the cup around the feces, the tube is partially filled with the float-or-sink liquid diluent, the feces and the diluent are mixed together using a wooden stick supplied with the kit, the piston, held by its handle, is inserted into the open top of the cup and pressed downward compressing much of the feces material as a cake on the bottom face of the piston, while the liquid and some of the ova pass through the perforations of the piston into the space above. The length of the piston's handle is short enough that when the piston "bottoms," the top of the handle is entirely inside the receptacle. If the volume of the original feces sample and of the added diluent were not too great, the top of the handle is not quite submerged in the mixture and the finger of the operator is not contaminated. Additional diluent is then added to fill the tube barely to over-flowing, forming a meniscus at the top into which the ova from the space above the piston collect within a few minutes. By laying a microscope slide cover glass on the meniscus, a drop of liquid with its collected ova is picked up, and under the microscope the number and kind of ova can be visually determined.